Hydrostatic extrusion system



March 24, 1964 G. GERARD ETAL 3,126,096

HYDROSTA'IIC EXTRUSION SYSTEM Filed May 4, 1961 3 Sheets-Sheet 1 FIGtheir gram/5Z3 March 24, 1964 Y s. GERARD ETAL 3 ,126,096

HYDROSTATIC EXTRUSION SYSTEM 3 Sheets-Sheet 2 Filed May 4, 1961 mmvgoxs.GERARD a RAYMAN GEORGE FIG 4 their AT T OR/VE Y5 March 24, 1964 ca.GERARD ETAL 3,126,096

' HYDROSTATIC EXTRUSION SYSTEM Filed May 4, 1961 3 Sheets-Sheet 3 FIG 3INV EN TORS.

az s sszmza &

B y 6 I Fl glMQ iheir ATTORNEYS United States Patent 3,126,896HYDROSTATIC EXTRUSION SYSTEM George Gerard, Yonkers, and Jacob Brayman,Staten Island, N.Y., assignors to Barogenics, Inc., a corporation of NewYork Filed May 4, 1961, Ser. No. 107,836 11 Claims. (Cl. 207-6) Thisinvention relates generally to methods and apparatus for extrudingmaterial such as ferrous and nonferrous metals, plastics, stone, or thelike. More particularly, this invention relates to methods and apparatusin which hydrostatic pressure is used to extrude such material.

In present day commercial practice, materials such as brass, aluminum,mild steel, and other low strength materials are extruded in a manner asfollows. A cylindrical billet of the material is placed within a closefitting tubular container having an open rear end and having at itsfront end a stationary extrusion die. For so called hot extrusion, thebillet as placed in the container is at an elevated temperature topromote the extrusion thereof through the die. Moreover, to the end ofreducing friction between the billet and the container wall, the billetis usually coated with a lubricant.

Extrusion is effected by inserting a ram into the container behind thebillet, and by driving the ram inwardly under great force until thepressure within the billet builds up to the point where the materialtherein becomes sufficiently plastic to flow through the die.

While the above-described conventional extrusion technique is the besthitherto known to the art for commercial use, it has numerousdisadvantages as follows. First, in spite of the use of a solid orviscous lubricant around the billet, during most of the extrusion anappreciable amount of friction will exist between the billet and thecontainer wall for the reason among others that, early during theextrusion the pressure of the ram causes the billet to bulge radially tosqueeze out through the die most of the lubricant interposed between thebillet and the container wall. Therefore, a great amount of the tonnageused in forcing the billet forward must be expended merely in overcomingthe substantial frictional eifect around the billet circumference.

Second, because of the described friction between the billet and thecontainer wall, in most of the billet the radial distribution ofpressure is not truly hydrostatic. Instead, except at its rear end wherethe billet is flatly contacted by the ram, the radial pressuredistribution in the billet is such as to peak in the center and to falloff towards the outer edges where the billet is able to sustain shearstresses because of its contact with the wall of the stationarycontainer. As a result of this uneven radial pressure distribution, itis necessary to supply energy to the ram which is substantially inexcess of the theoretical amount of energy needed to extrude the billet.

Another factor necessitating a ram pressure much in excess of thattheoretically needed, is that, due to the described friction between thebillet and the container wall, and due, further, to radial bulging ofthe billet under the pressure applied thereto and to consequent radialbulging of the container, the axial distribution of the pressure withinthe billet is not uniform. Specifically, over the length of the billetthe pressure therein drops from a maximum pressure at the billet-raminterface toa front end pressure which may be, say, only about one tenthof such maximum pressure when the billet is of its original length. Itfollows that, to build up the pressure in the front end of the billet tothe critical value required at such front end to produce flow of thebillet material through 3,126,096 Patented Mar. 24, 1964 the die it isnecessary to exert a much larger pressure on the rear end of the billet.

Fourth, the ram pressure required at the rear end of the billet toproduce extrusion thereof is a pressure which is a function of theunextruded length of the billet. That is, as, during extrusion, theunextruded length of the billet progressively decreases, the rampressure required first drags and then climbs again. The result of thisphenomenon is that at the beginning and towards the end of theextrusion, greater pressures are required to be exerted by the ram thanwould normally be expected from the maximum shear stress properties ofthe billet material. In fact, the ram pressure required for extrusionfinally increases so much that it virtually becomes impossible toextrude the entire billet. Therefore, the extrusion usually terminateswith a butt of the billet being left in the container and requiringremoval before the next extrusion cycle.

Fifth, although at the beginning of the extrusion cycle, the die iscoated with a solid or other lubricant, during the early part of theextrusion, this lubricant is, as stated, washed out with the extrudedmaterial, so as soon to leave the die bare. Thereafter, the passage ofthe billet material through the unlubricated \die exposes it to highabrasive and frictional forces which materially reduce the life of thedie.

In an attempt to overcome the above-noted disadvantages accompanyingconventional extrusion, experimental efforts have been made to produceextrusion of a billet through a die in stationary relation to the billetcontainer by employing a hydraulic fluid disposed in the containeraround the billet to generate the extruding pressure.

Thus, in volume 1, No. 11 of the Russian publication, Journal ofEngineering and Physics, the article at pages. -109 thereat reports on ahydrostatic extrusion apparatus of the sort just described in which apump is employed to pressurize fluid which is thereafter introducedthrough a small pipeline into the billet container behind the billet.Such arrangement is not, however, adapted for practical use becauseknown pumps are incapable of generating the high hydrostatic pressuresrequired for extrusion of most materials, and because, once theextrusion starts, it proceeds with considerable speed, and the smalldiameter pipeline connecting the pump with the billet container cannotsupply sufiicient liquid to keep the hydrostatic pressure at a constantlevel.

In another proposal for hydrostatic extrusion made by T. W. Bridgman, onpages 177-179 of his text Large Plastic Flow and Fracture (published byMcGraw-Hill in 1952), the hydraulic fluid in the billet container ispressurized by the inward driving of a ram inserted into the bore of thecontainer at the end thereof away from the stationary die. This latterproposal is, like the earlier discussed Russian one, not adapted forcommercial use because the Bridgman apparatus cannot be scaled up toaccommodate billets of commercial size and because of various otherconsiderations.

It is accordingly an object of the invention to provide hydrostaticextrusion methods and apparatuses which are free of the above-describeddisadvantages accompanying conventional extrusion, and which are free,also, of the above described limitations of the experimental effortshitherto made in hydrostatic extrusion.

Other objects of the invention are to eliminate billetwall interfacefriction, to increase die life, and to permit the use of much greaterenergy in extruding the billet.

Another object of the invention is to provide extrusion methods orapparatuses, hydrostatic or otherwise, in which the extrusion of billetmaterial is reverse in the sense that the direction of extrusion of thematerial is opposite to that in which the ram or other exterior agencyacts to produce the extrusion.

Still another object of the invention is to provide extrusion apparatus,hydrostatic or otherwise, in the form of a compact unit which isself-containing of the forces generated during the extrusion process.

These and other objects are realized according to the invention byemploying a tubular billet container in which the bore is closed at oneend and is plugged at the other end by an extrusion die means disposedinside the bore and adapted to be forced therein towards the closed endthereof. Such die means and the part of the bore inward of such diemeans form a chamber for containing a billet and, preferably, also, ahydrostatic pressure transmitting medium filling an interspace formedbetween the billet and the bounding wall surface of the bore of thecontainer. To produce extrusion, the die means inside the bore is drivenunder extreme force towards the closed end of the bore so as to cause tobe developed in the billet an internal pressure sufiicient to produceflow of the billet material through the opening of the die means in adirection the reverse of that in which the die means is driven.

For a better understanding of the invention, reference is made to thefollowing description of an exemplary embodiment thereof, and to theaccompanying drawings wherein:

FIGURE 1 is an isometric view in vertical cross-section of the mentionedembodiment;

FIGURE 2 is an enlarged view in vertical cross-section of a portion ofthe embodiment of FIGURE 1;

FIGURE 3 is a view in vertical cross-section of a modification of theembodiment of FIGURE 1; and

FIGURE 4 shows some exemplary working dimensions for the variouselements of the FIGURE 1 embodiment.

Referring now to FIGURE 1, a pressure containing vessel has at its lowerfront end a flange 11 encircling a bore 12 formed in the vessel to beopen at the lower end of the vessel, and to extend upwardly from thatopen end. The word bore is used herein as descriptive of the structureof the central hollow space of vessel 10 rather than as descriptive ofits origin. Thus, the bore 12 need not be a hole formed by boring, but,instead, may be formed, say, by machining out the interior of a casthollow vessel 10.

As shown in FIGURE 1, the bore 12 extends upwardly only partway throughvessel 10 so that the top 13 of the bore is closed off by an end portion14 of vessel 10 which is integral with the rest of the vessel. Ifdesired, however, the pressure containing vessel may be of a type inwhich the interior bore extends through the vessel from end to endthereof and in which the top of the bore is closed off by a removableend closure. Thus, for example, the bore 12 may be closed at its top bya closure means similar to one of those disclosed in our copendingapplication, Serial No. 833,420, filed August 13, 1959, now U. S. PatentNo. 3,063,594 issued on November 13, 1962.

The flange 11 of vessel 10 registers with a flange 15 disposed at theupper end of and forming an integral part of a piston housing 16. Suchhousing contains hydraulic cylinder 17 co-axial with and of greaterdiameter than the bore 12. As shown, the cylinder 17 extends upwardly inhousing 15 towards bore 12 from a cylinder bottom 18 formed by an endportion 19 of the housing 16 integral with the rest of the housing. Anadapter tube 20 with a hollow axial core 21 extends upwardly through theend portion 19 to project into cylinder 17 beyond the bottom 18 thereof.

Received with a sliding fit in cylinder 17 is an annular piston 25having a central cylindrical hollow space 26 in which the adapter tube20 is in turn received with a sliding fit. The piston 25 has formed inthe exterior circumference thereof an annular groove 27 in which thereis an O ring 28 providing a pressure seal between the piston and thewall of cylinder 17. In like manner, the piston 25 has formed in theinterior circumference thereof an annular groove 29 in which there is anO ring 38 providing a pressure seal between the piston and the wall oftube 20. A conduit 31 passing through the bottom portion 19 of housing16 permits injection of pressurized hydraulic fluid into cylinder 17behind piston 25'.

Mounted coaxially on piston 25 is a ram 35 of lesser diameter than thepiston 25, the said ram 35 being comprised of a head 36 and a stem 37.The ram extends upwardly from the piston to have the front end of theram received with a sliding fit in the open end of the bore 12 of vessel10. The ram plugs such open end so that the ram cooperates with the partof the bore inwards of the ram to form a billet container chamber 38.Communicating with that chamber is a coaxial passageway 39 extendingthrough the length of ram 35 from a lower juncture with space 26 insidepiston 25 to an upper orifice 40 by which the passageway opens into thelower end of chamber 38. The chamber 38 is otherwise rendered pressuretight at its lower end by an O ring 41 seated in an annular groove 42formed in the head 36 of the ram, the ring 41 bearing against thecircumferential wall of bore 12 to form a pressure seal.

While the arm 35 may be made integral with piston 25, preferably the rammerely rests on the piston so that the ram is free to find its naturalposition within bore 12 during an extrusion operation. Means other thanthe shown hydraulic cylinder and piston combination may be employed todrive the ram into the bore. Thus, for example, the housing 16, piston25 and tube 20 may be dispensed with, and the ram 35 may be driven intobore 12 by placing the assembled combination of vessel 10 and ram 35between the platens of a conventional hydraulic press to allow the ramto be driven into the vessel by the closure towards each other of suchplatens.

The chamber 38 is shown in FIGURE 1 as containing (1) a lesser sizedbillet 45 having its lower end seated over orifice 40 in the head 36 ofram 35, and (2) a volume of a hydrostatic pressure transmitting medium46 filling the interspace in chamber 38 between the billet and the wallsurface of bore 12 which bounds chamber 38. Thus, the medium 46 entirelysurrounds the billet except the end of the billet which is seated on theram. For cold extrusion, the medium 46 may be a hydraulic fluid such aswater, alcohol, oil or the like. When, however, the billet as containedin chamber 38 is at an elevated temperature (produced either by heatingof the billet prior to its insertion in the chamber or by heating thebillet in some manner within the chamber itself), the medium 46 ispreferably comprised of temperature resistant material such as a metalwith a low melting point or a glass with a similar low melting point andin the form of, say, glass fibers packed around the billet. It is notobjectionable for the medium 46 to be comprised of a material which is anon-plastic solid at room temperature and atmospheric pressure so longas such material becomes plastic to transmit pressure in a hydrostaticmanner under the pressure and temperature conditions employed to produceextrusion of the billet from the chamber 38.

A fluid medium 46 may be introduced through the top of vessel 10 intochamber 38 by a simple valve system as follows. A cylindrical duct 50 ofsmall diameter is formed in vessel 10 to pass upwardly from chamber 38through the top portion 14 of the vessel into a larger diametercylindrical well 51 formed in that top portion. Seated in the chamber 38is a valve head 53 having an annular gasket 54 on its upper side. Thehead 53 is connected to the bottom of a valve stem 55 which passes witha sliding fit upwardly through duct 50 to project into Well 51 and tothere engage threadedly with a nut 56 of greater diameter than duct 50.Formed in stem 55 is a keyway 57 extending lengthwise in that stem froma point just above head 53 to the top of the stem. Thus, the keyway 57passes through the nut 56.

To inject fluid into chamber 38, the nut 56 is unscrewed to allow thestem 55 and attached head 53 to drop so as to open up a space betweenthe gasket 54 and the top 13 of the chamber 38. Fluid is then pouredinto well 51 to pass from that well through keyway 57 into chamber 38.When the chamber has been filled with fluid, the nut 56 is retightenedto draw the gasket 54 up against the top 13 of the chamber.

The chamber 38 may be filled with the medium 46 in ways other than thatjust described. Thus, in the event, it is desired to use a medium whichis a solid at room temperature and atmospheric pressure, the FIGURE 1apparatus may be constructed so that it is upside down in relation toits showing in FIGURE 1, a layer of the solid material may be packed inbore 12 against portion 14 of the vessel to a thickness equal to thedesired clearance between the upper end of the billet and the endsurface 13 of the bore, the billet may then be inserted in the bore torest in properly centered relation on such layer, more material may bepacked into the bore to fill up the space between the cylindrical wallthereof and the billet, and, finally the ram may be inserted in thebore. Moreover, either a solid or a fluid medium may be introduced inthe chamber 38 by constructing vessel so that, as described, the bore 12extends all the way through the vessel, and the top of the bore isplugged in a pressure-tight manner by an end closure which is removableto permit the filling of the chamber 38 from the top. In FIG. 1, theshell formed around bore 12' by vessel 10 evidently acts as a housingfor the billet and for the medium which surrounds the billet. I Duringan extrusion operation, the vessel 10 and the piston housing 16 areclamped together by a split ring clamp formed of two identicalsemi-circular halves 60 of which one appears in FIGURE 1. To assure thatthe two halves of the clamp do not become separated, a safety ring 61 isplaced around the clamp. The clamp and safety ring may be constructed inaccordance with the teachings in our aforementioned US. Patent No.3,063,594. As alternatives to the use of split ring clamp, the vessel 10and housing 16 may be bolted, bayoneted or keyed together.

FIGURE 2 shows the details of the head 36 of ram 35. This head is, infact, a die means or die assembly comprised of an upper annular primarydie 70, a lower annular secondary die 71, and an annular die holder 72disposed below die 70 and around die 71. To relate the presentlydescribed assembly to come of the previously described features ofVessel 10, it is the central opening through primary die 70 which formsthe orifice 40 by which the passageway 39 in ram 35 opens into thebillet container chamber 38. Moreover, it is the die holder 72 whichacts as the carrier for the previously described groove-and-ringpressure seal 41, 42 by which fluid is prevented from leaking out ofchamber 38 through the circumferential interface between the dieassembly and the cylindrical wall of bore 12. The elements 763-72 of thedie assembly are fastened together and to the stem 37 of the ram 35 byconventional securing means (not shown) as, say, bolts. The secondarydie 71-needs no particular securing means since such die is entirelyconstrained by the primary die 70, the die holder 72 and the ram stem37. If desired, the die assembly need include only a single die insteadof the two dies '70 and 71.

The bottom face 80 of the billet 45 and the top face 81 of the primarydie 70 are matched incontour to make flat contact with each other overan annular area disposed radially outward of the orifice 40. Thisannular area of contact forms -a seal which prevents hydraulic fluid 46in the interspace around the billet from leaking underneath the billetinto orifice '40 and thence out passageway 39. The integrity of suchseal depends, of course, upon the contact pressure between the billetand the primary die. While the weight of the billet is, alone, enough tomaintain the integrity of the seal, the tightness of the seal is furtherincreased when the hydraulic fluid 46 is pressurized in the course ofeffecting an extrusion of the billet. This is so, because of thefollowing. As shown, the annular area of contact between the billet andthe primary die 70 is less than the area (FIG. 1) of the top of thebillet. Hence, when the fluid 46 becomes pressurized, should any of thisfluid leak into the interface between the billet and the primary die,the greatest force which such fluid can exert upwardly on the billet isequal to the fluid pressure times the area of contact between the billetand the primary die. On the other hand, the downward forcesimultaneously exerted on the top of the billet is equal to the samefluid pressure times the area of the billet top. The latter area is,however, evidently greater than the mentioned area of contact.Accordingly, when the fluid 46 is pressurized, such fluid exerts on thebillet a net downward force which increases as the pressure increases.Thus, the seal provided ,by the contact .between the billet and theprimary die is one which is characterized by a self-tightening effect.

As shown, the billet 45 has formed at the front end thereof acylindrical stub which projects, into the orifice 40. This stub servesboth to center the billet in relation to the die assembly in the courseof setting up the apparatus and to provide a leader into the die duringthe extrusion process.

The FIGURE 1 apparatus is set up for cold extrusion in the followingmanner. With the safety ring 61, the split ring clamp 60 and the vessel10 being removed from the housing 16, with the piston 25 being at thebottom of the hydraulic cylinder '17, and with the ram 35 upstandingfrom the piston as shown, a billet 45 of material to be extruded isseated in centered relation on the ram 35. The vessel 10 is then placedover the housing 15 so that the flange 11 of the vessel and the flange15 of the housing are in registration, and so that the ram and thebillet thereon slip into the bore 12 of the vessel. Next, the ring clampis assembled to lock together the flanges 11, 15 and thesafety ring 61is placed around the assembled ring clamp. Finally, the chamber 38within bore 12r is filled with hydrostatic fluid in the mannerheretofore described through the valve system at the top of the vessel.The apparatus is now ready to operate.

The extrusion operation is initiated by injecting hydraulic fluidthrough conduit 31 into cylinder 17 behind piston 25 so as to drive thepiston upwardly. The pressure of the fluid injected behind the pistonmay be of the same order as that commonly used in the present dayhydraulic art, i.e., between 10,000 p.s.i. and 50,000 psi. In the view,however, that the face area of piston 25 is greater by, say, tenfoldthan the face area of ram 35, the driving pressure behind the piston isconverted by a pressure multiplying action into a much higher pressureexerted by the head of the ram 35 on the fluid 46 in the chamber 38.Thus, the pressure ultimately developed in fluid 46 by the ram may be onthe order of from 100,000 p.s.i. to 500,000'p.s'.i.

As the ram 35 is driven by piston 25 into the bore 12, the ramautomatically compacts the fluid 46 to build up the hydrostatic pressuretherein to the critical value required to initiate extrusion of billetmaterial through the die assembly 36. During this build up ofhydrostatic pressure, the forward movement of the ram lifts the billetso that the top thereof moves towards the valve head 53. Suflicientclearance is, however, provided between the top of the billet and thevalve head so that the critical hydrostatic pressure value is reachedwell before the top of the billet strikes the valve head. Thus, it willbe seen that the ram does not at any time exert any direct pressure onthe billet.

' The critical hydrostatic pressure value is reached when the pressureexerted on the billet by the fluid 46 renders the billet materialsufficiently plastic to start to flow into the die assembly andthereafter, through, in order, the rest of passageway 39, the space 26inside piston and the hollow core 21 of adapter tube 20 to be finallyejected from the apparatus. Once this critical pressure has beenreached, and extrusion of the billet material begins, the furtheradvancement of ram into bore 12 merely maintains the pressure in fluid46 at this critical value, and the extrusion of the billet material iscontinuous until all of the billet has been extruded. Once the billethas been fully extruded, the fluid 46 escapes from chamber 38 throughpassageway 39 the pressure of the fluid in chamber 38 drops to anegligible value, and the extrusion run is terminated.

Because, during extrusion, the fluid 46 exerts pressure on the billet onall sides excepting at the front end thereof, throughout the volume ofthe billet the pressure therein is substantially hydrostatic anduniform. Hence, at substantially 'all points in the billet the materialthereof is characterized to the same degree by that desired condition offull plasticity which is required for the billet material to flowthrough the opening of the die assembly. With all the material of thebillet thus being in this fully plastic condition, the combination ofthe pressure exerted by fluid 46 downward on the billet and the pressureexerted by such fluid inwardly on the billet, particularly all aroundits base but also all around the rest of the circumference of thebillet, the pressurize fluid has on the billet material an ideal guidingor channeling affect whereby, throughout the extrusion run, the billetmaterial flows freely and in the path of least resistance towards theopening of the die assembly. Two desirable consequences of such actionsby the pressurized fluid 46 of rendering the billet material fully anduniformly plasticized and of channeling such material to so flow towardsthe die assembly opening are (1) the entire billet may be extruded sothat no butt is left over at the end of the run, (2) the billet may beof substantially greater diameter than the die assembly opening.

Some other advantages of the described hydrostatic extrusion method areas follows.

Because the billet is separated at all times by fluid 46 from the wallof bore 12, there is no billet-wall interface friction whatever.Moreover, fluid 46 provides an excellent lubricant for the billet. Thisis so, because as the billet material passes through the die assembly,there is carried with such material a thin film of fluid which clings tothe material being extruded to act as a lubricant between it and the diefaces. There is always more than enough fluid 46 in the chamber 33 toprovide such fluid lubricating film. Accordingly, the die assembly'iseffectively lubricated throughout the whole extrusion run, and the lifeof the die assembly is thereby maximized.

In conventional extrusion (l) the diameter of the ram must beapproximately the same as that of the billet, 2) the length of the rammust be short enough in relation to its diameter to avoid buckling ofthe ram under the force applied thereto to effect extrusion of thebillet, (3) the maximum stroke of the ram is limited by its length, (4-)the volume of billet material which can be extruded by the ram islimited by its stroke and is roughly equal to such stroke times the ram(or billet) diameter. Therefore, in conventional extrusion, as thediameter of the billet decreases, the volume of extruclable billetmaterial decreases as the square of such diameter.

In the above described hydrostatic extrusion method, on the other hand,after the hydrostatic pressure in the chamber 38 has reached the valueat which extrusion begins to take place, all that is required to fullyextrude a billet of given diameter is that the volumetric displacementof the chamber be decreased in an amount equal to the volume of thebillet. Such decrease in the volumetric displacement of chamber 38 neednot, however, be obtained by a ram stroke approximating the length ofthe billet. Instead, it can be obtained by using a chamber substantiallygreater in diameter than the billet, and by using a ram which issubstantially shorter than the billet length and which, therefore has astroke substantially shorter than that length. Thus, the describedhydrostatic method permits the use of a ram which is stubby relative tothe length of the billet to be extruded, and which, because of itsstubbiness, is capable, without buckling, of extruding a much greatervolume of billet material than if the diameter and length of the ram hadto be proportioned to respectively, the diameter and length of thebillet.

To state what has just been said in another way, in the describedhydrostatic method the critical factor is the value of hydrostaticpressure required for extrusion, since such value determines the ratioof ram diameter to ram length which must be used to assure that the ramwill not buckle in the course of building up the hydrostatic pressure inthe billet containing chamber to that required value. Further, assuminga certain required value of hydrostatic pressure and a ram having adiameter length ratio determined by such value, and having a givendiameter and length which are in accordance with such ratio, evidently(in order to fit into the chamber) the billet must be of less diameterthan the ram, and, also, (if full extrusion of the billet is desired),the total volume of the billet must be less than the product of the ramsdiameter and stroke. Subject, however, to the limitations justenumerated on the maximum diameter and volume of the billet, the ram andassociated chamber (when the latter is of suitable shape) are capable ofextruding a billet of any diameter and volume whatever less than thelimiting diameter and volume, whereas this is not true of the ram andchamber employed in conventional extrusion.

In the described apparatus, while the pressurizing of fluid 4s tends toproduce radial bulging of the circumferential wall of bore 12, anyresulting tendency of the pressure seal provided by the 0 ring 41 toopen up is largely counteracted by the thick flange 11 around the mouthof the bore. Such tendency to open up is further counteracted duringextrusion by the extruded material which, as it passes through the dieassembly, is highly compressed to exert on the interior of the assemblya force directed radially outward and tending to expand the assembly tomore firmly seat the ring 41 against the wall of the bore.

As will be noted, the die assembly is fully supported during extrusionby the ram stem 37. Because of the excellent support so provided for thedie assembly on the side thereof opposite the high pressure generated inchamber 3, there can be eliminated from the FIGURE 1 apparatus the extraelement of the massive stationary support which is usually needed inconventional extrusion apparatus to assure that the die assembly doesnot fail under such pressure. Moreover, inasmuch as the ram stem isdriven by the piston 25 to provide a dynamic type of support for the dieassembly, any deflection of deformation of such assembly under pressureis much reduced compared to what it would be if such pressure were to beopposed only by the passive support action of a stationary support.

The location in the FIGURE 1 apparatus of the die assembly at the sameend of the container vessel as the ram allows tire vessel and thehydraulic cylinder and piston assembly or other ram drive means to bejoined together, in say, the manner shown without requiring the use toeffect such joinder of any tie rods of like extraneous structuralelements prone to mechanical failure. The vessel and ram drive means asso joined together form a compact structural unit in which all forcesgenerated in the unit during extrusion are contained therewithin insteadof being communicated to an exterior bed or frame.

Referring now to FIGURE 3, the elements of the modification showntherein which are counterparts of those of the FIGURE 1 embodiment areeach designated by the same reference numeral as the corresponding FIG-URE 1 element but are further designated by a prime sufiix. Thedifferences between the FIGURE 1 embodiment and the FIGURE 3modification are as follows. In the modification, a bore 12. is formedin a piston 25' so that the element 25 acts as the billet containervessel as well as the piston. Further, a ram 35' is turned upside downto have its head 35 inserted in the upper end of the bore, and theflanged element 16 is replaced by a similarly flanged ram housing 90having an upper transverse portion 91 adapted to act as a stop for theback end of the ram stem 37'. Formed in this portion 91 coaxial with apassageway 39' in the ram is a hole 92 permitting escape to the exteriorof housing 90 of billet material extruded through such passageway.

The FIGURE 3 apparatus is set up as follows for an extrusion operation.With the safety ring 61', shown split ring clamp 60, housing 90, and ram35 being removed, a billet 45 is placed in bore 12' so that a guide rod95 upstanding coaxially from the bottom of the bore is slidably receivedwithin a matching guide hole 96 formed in the bottom of the billet. Acompression spring 97 encircling rod 95 maintains the billet anappropriate distance from the bottom of the bore. After the billet hasso been placed in the bore, hydrostatic fluid 46 is introduced into thebore until the surface of the fluid is level with or slightly higherthan the upper end of the billet. Next, the ram 35 is fitted into bore12 and advanced therein until the head of the ram makes, as earlierdescribed, a fluid sealing contact with the rear end of the billet.During such advancement but before such sealing contact is made, anyexcess of fluid in bore 12' will be forced around the billet intopassageway 39. The assembly of the apparatus is completed by addinghousing 90, split ring clamp 60 and safety ring 61'. As shown in FIGURE3, the spring 97 in bore 12' is of a size and resiliency to position thebillet and ram so that, statically, there is a slight clearance betweenthe upper end of ram stem 37 and the underside of portion 91 of housing90.

In the operation of the FIGURE 3 apparatus, hydraulic fluid is injectedthrough conduit 31' to advance the piston 25' to bring the upper end ofram stem 37 into contact with the stop portion 91 of housing 90.Thereafter, the operation of the FIGURE 3 apparatus is essentially thesame as the previously described operation of the FIG- URE 1 apparatus.

The FIGURE 3 apparatus has the same advantages as those of the FIGURE 1apparatus. Moreover the FIG- URE 3 apparatus has the additionaladvantage that the pressure of the piston-driving fluid in theinterstitial space below ring 28 between piston 25' and the wall ofcylinder 17 exerts on the piston a pressure adapted to reduce radialbulging of the circumferential wall of bore 12' in the manner taught inour copending application Serial No. 35,933 of 1960 filed June 14, 1960,now U.S. Patent No. 3,049,756 issued on August 21, 1962.

In the FIGURE 1 apparatus, the elements 10, 16 and 60 may be made ofalloy steel, the elements 25 and 61 may be made of carbon steel and thedie assembly 7G 72 may be made of tool steel. Like elements of theFIGURE 3 apparatus may be likewise constructed. Some exemplary workingdimensions for the FIGURE 1 apparatus are shown in FIGURE 4. The FIGURE3 apparatus may be constructed to the same scale.

The above described apparatus of FIGURE 1 and of FIGURE 3 beingexemplary only, it will be understood that additions, omissions andmodifications thereto may be made without departing from the spirit ofthe invention, and that the invention hereof comprehends embodimentsdiifering in form and/or detail from those which have been specificallydescribed. Thus, for example, V type packings may be used in place ofthe 0 rings which have been disclosed. Accordingly, the in vention isnot to be considered as limited save as is consonant with the recitalsof the following claims.

-We claim: a

1. Apparatus comprising, a pressure containing vessel with an interiorbore operably open only at one end of said vessel, a single inwardlymovable ram projecting into said bore to have a sliding fit therewithand to plug the open end thereof so as to form with the part of saidbore inwards of said ram a chamber adapted to contain a billet inabutting relation with said ram and in spaced relation from the wallsurface of said bore, and adapted to contain also a hydrostatic pressuretransmitting medium filling the interspace between said wall surface andbillet, said ram having extending lengthwise therethrough a passagewaycharacterized at its chamber end by an orifice over which said billet isadapted to be seated, means to drive said ram into said bore so as todevelop in said medium a hydrostatic pressure producing extrusionthrough said passageway of billet material, die means forming part ofsaid ram and disposed around said pas sageway to shape the extrudedbillet material, and annular sealing means disposed around said ram inthe interspace between the exterior circumferential surface of said ramand the surrounding wall of said bore to provide in said interspace aseal obstructing leakage of said medium past said ram out of the openend of said bore.

2. Apparatus as in claim 1 further comprising pressurerestraining meansin the form of a flange selectively positioned at said end of saidvessel and disposed around said end to oppose radial enlargement of theopen end of said bore by the pressure of said medium.

3. Apparatus comprising, first housing means having therewithin a boreoperably open only at one end of said means, an inwardly movable ramhaving a stem portion and a head portion of which the latter projectsinto said bore to plug the open end thereof so as to form with the partof said bore inwards of said ram a billet containing chamber, said ramhaving extending lengthwise therethrough a passageway for extrusion ofbillet material from said chamber, second housing means enclosing thestem portion of said ram and disposed opposite said end of said firsthousing means, threadless coupling means including shoulder meansdisposed circumferentially about each of said housing means, saidthreadless means coupling said first and second housing means end to endto provide an enclosure formed or" said two housing means, and means insaid enclosure to drive said ram into said bore to produce extrusion ofsaid material through said passageway, said enclosure being selfcontaining of the forces generated therein during said driving of saidram.

4. Apparatus comprising, a pressure containing vessel having flangemeans at its front end and having an interior bore operably open only atsaid end, an inwardly movable ram projecting into said bore to plug theopen end thereof so as to form with the part of said bore inwards ofsaid ram a billet containing chamber, said ram having extendinglengthwise therethrough a passageway for extrusion of billet materialfrom said chamber, a housing disposed opposite said front end of saidvessel and having flange means registering with the flange means of saidvessel, means in said hon-sing to drive said ram into said bore toproduce extrusion of material through said passageway, and ring meansclamping said two flange means together to form of said vessel andhousing a unit which is self containing of the forces generated thereinduring said driving of said ram.

5. Apparatus comprising a pressure containing vessel having flange meansat its front end and having an interior bore operably open only at saidend, an inwardly movable ram projecting into said bore to plug the openend thereof so as to form with the part of said bore in- Wards of saidram a chamber adapted to contain a billet in abutting relation with saidram and in spaced relation from the wall surface of said bore, andadapted to contain also a hydrostatic pressure transmitting mediumfilling the interspace between said wall surface and billet, sald ramhaving extending lengthwise therethrough a passageway characterized atits chamber end by an orifice over which said billet is adapted to beseated, a housing disposed opposite said front end of said vessel andhaving flange means registering with the flange means of said vessel,means in said housing to drive said ram into said bore, to develop insaid medium a hydrostatic pressure producing extrusion through saidpassageway of billet material, die means forming part of said ram anddisposed around said passageway to shape the extruded billet material,and ring means clamping said two flange means together so as to form ofsaid vessel and housing a unit which is self containing of the forcesgenerated therein during said driving of said ram.

6. Apparatus comprising a pressure containing vessel with an axiallyextending interior bore operably open only at one end of said vessel, ahousing disposed opposite said end of said vessel and containing ahydraulic cylinder coaxial with and of greater diameter than said boreand opening towards said bore, an adapter tube extending through saidhousing in coaxial relation with said cylinder to project thereintobeyond the bottom thereof, an annular piston slidably received in saidcylinder and having a central space in which said tube is slidablyfitted, a ram projecting coaxially from said cylinder into said bore toplug the open end thereof so as to form with the part of said boreinwards of said ram a billet containing chamber, said ram having formedcoaxially therethrough a passageway communicating between said chamberand said central space, and means to inject pressurized hydraulic fluidin said cylinder behind said piston to drive said ram into said bore soas to produce extrusion of billet material from said chamber throughsaid passageway, central piston space and adapter tube.

7. The method of extruding a billet comprising the steps of placing saidbillet in a tubular container with a bore operably closed at one end andopen at the other and larger in both longitudinal and cross sectionaldimensions than said billet so that said billet is disposed to beeverywhere in spaced relation from the wall surface bounding said bore,filling the interspace between said billet and wall surface with ahydrostatic pressure transmitting medium, plugging the open end of saidbore by an extrusion die means slidably received in said bore to abutthe near end of the billet therein, and forcing said die means towardsthe closed end of said bore so as to develop in said medium ahydrostatic pressure producing extrusion through said die means ofbillet material.

8. Apparatus comprising, a housing containing a hydraulic cylinder, apiston slidably received in said cylinder and having formed therein anaxial bore of which the end towards the front of the cylinder is openand of which the other end is operably closed, a ram slidably receivedin said bore to plug the open end thereof so as to form with the part ofsaid bore inwards of said ram a chamber adapted to contain a billet inabutting relation with said ram and in spaced relation from the wallsurface of said bore, and to contain also a hydrostatic pressuretransmitting medium filling the interspace between said wall surface andbillet, said ram having extending lengthwise therethrough a passagewayterminated at said chamber end by an end over which said billet isadapted to be seated, means providing a stop behind said ram, means toinject fluid into said cylinder behind said piston to move it forwardlyso as to bring said ram in contact with said stop, and, thereafter todrive said ram into said bore so as to develop in said medium ahydrostatic pressure producing extrusion through said passageway ofbillet material, and die means forming part of said ram and disposedaround said passageway to shape the extruded billet material.

9. Apparatus comprising, first housing means having therewithin a boreoperably open only at one end of said means, an inwardly movable ramhaving a stern portion and a head portion of which the latter projectsinto said bore to plug the open end thereof so as to form with the partof said bore inwards of said ram a billet-containing chamber, said ramhaving extending lengthwise therethrough a passageway for extrusion ofbillet material from said chamber, second housing means disposedopposite said end of said first housing means and enclosing said stemportion of said ram, means including a hydraulic cylinder in one of saidhousing means and a piston in said cylinder for driving said ram intosaid bore to pro duce extrusion of said material through saidpassageway, said cylinder and piston being of larger diameter than saidram to convert the hydraulic pressure which actuates said piston into agreater extrusion-inducing pressure exerted on said billet material insaid chamber, and means coupling said first and second housing means endto end to provide by said two housing means an enclosure for containingthe forces generated therein during said driv ing of said ram.

' 10. The method of extruding a billet comprising placing in the bore ofa tubular container both a billet of lesser dimensions than said boreand a hydrostatic pressure-transmitting medium disposed in said bore torender said billet separated by said medium from the wall surfacebounding said bore, said bore being operably closed at one end, andbeing plugged at the other end by an inwardly movable ram of greaterdiameter than the billet and carrying a die through which extends apassageway continued lengthwise through the ram, and driving said raminto said bore so as to develop in said medium a pressure producingextrusion of the billet material through said passageway and anaccompanying shaping of said material by said die.

11. The method of extruding a billet comprising, placing in the bore ofa tubular container both a billet of lesser dimensions than said boreand a hydrostatic pressure-transmitting medium disposed in said bore torender said billet separated by said medium from the wall surfacebounding said bore, said bore being operably closed at one end, andbeing plugged at the other end by an inwardly movable ram of greaterdiameter than said billet and carrying a die supported on the sidethereof away from said bore by the body of said ram, and said ram beingcharacterized by a passageway extending lengthwise therethrough andthrough said die, and driving said ram into said bore so as to developin said medium a pressure producing extrusion of the billet materialthrough said passageway and an accompanying shaping of said material bysaid die.

References (Iited in the file of this patent UNITED STATES PATENTS74,612 Shaw Feb. 18, 1868 1,963,675 Plainevaux et al June 19, 19342,558,035 Bridgman June 26, 1951 2,920,760 Genders Jan. 12, 19602,962,164 Scribner Nov. 29, 1960 FOREIGN PATENTS 476,793 Canada Sept.11, 1951 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PatentNO, 3,126,096 Mareh 24, 1964 George Gerard et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 7, line 27, for -"pressurize" read pre -s SuIlZed. column 8, line49, for "3" read 38 column 9, line 16, strike out "shown" and insert thesame after "the" in same line 16, same column 9.

Signed and sealed this 14th day of July 1964.

(SEAL) Attest:

EDWARD J BRENNER Commissioner of Patents ESTON G. JOHNSON AttestingOfficer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3, 126,096 March 24, 1964 George Gerard et a1.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 7, line 27, for "pressurize" read pr-6.3.4:" SUIlZGd column 8 li49 f n 1" read lumn line Strike Out "shown" and insert the same after"the" in same line 16, same column 9.

Signed and sealed this 14th day of July 1964.

(SEAL) Attest:

ESTON G. JOHNSON EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

1. APPARATUS COMPRISING, A PRESSURE CONTAINING VESSEL WITH AN INTERIORBORE OPERABLY OPEN ONLY AT ONE END OF SAID VESSEL, A SINGLE INWARDLYMOVABLE RAM PROJECTING INTO SAID BORE TO HAVE A SLIDING FIT THEREWITHAND TO PLUG THE OPEN END THEREOF SO AS TO FORM WITH THE PART OF SAIDBORE INWARDS OF SAID RAM A CHAMBER ADAPTED TO CONTAIN A BILLET INABUTTING RELATION WITH SAID RAM AND IN SPACED RELATION FROM THE WALLSURFACE OF SAID BORE, AND ADAPTED TO CONTAIN ALSO A HYDROSTATIC PRESSURETRANSMITTING MEDIUM FILLING THE INTERSPACE BETWEEN SAID WALL SURFACE ANDBILLET, SAID RAM HAVING EXTENDING LENGTHWISE THERETHROUGH A PASSAGEWAYCHARACTERIZED AT ITS CHAMBER END BY AN ORIFICE OVER WHICH SAID BILLET ISADAPTED TO BE SEATED, MEANS TO DRIVE SAID RAM INTO SAID BORE SO AS TODEVELOP IN SAID MEDIUM A HYDROSTATIC PRESSURE PRODUCING EXTRUSIONTHROUGH SAID PASSAGEWAY OF BILLET MATERIAL, DIE MEANS FORMING PART OFSAID RAM AND DISPOSED AROUND SAID PASSAGEWAY TO SHAPE THE EXTRUDEDBILLET MATERIAL, AND ANNULAR SEALING MEANS DISPOSED AROUND SAID RAM INTHE INTERSPACE BETWEEN THE EXTERIOR CIRCUMFERENTIAL SURFACE OF SAID RAMAND THE SURROUNDING WALL OF SAID BORE TO PROVIDE IN SAID INTERSPACE ASEAL OBSTRUCTING LEAKAGE OF SAID MEDIUM PAST SAID RAM OUT OF THE OPENEND OF SAID BORE.